Li Tie, a 52-year-old essayist from Wuhan was given ten years for subverting state power. Two other men, Chen Wei, 42, and Chen Xi, 45, were handed jail terms of a similar length either side of Christmas.

All three had previous convictions, accounting in part for the severity of the sentences. A fourth man, a poet named Zhu Yufu, was charged with subversion on Monday.

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Mr Liu said the Arab Spring continues to unnerve Beijing and that the current repression “is more to do with international affairs than problems inside China”. He added: “Local governments have been told by Beijing they can lock up anyone who seems like a troublemaker. Then they go back two or three years and trawl the records for anything that might implicate them.”

He added that the government was more worried about petitioners, people bringing specific grievances to Beijing, than about dissidents this year.

Meanwhile, Yu Jie, an activist whose family was allowed to leave China earlier this month, gave a graphic description of the house arrests and torture he had suffered after his friend, Liu Xiaobo, was awarded the Nobel peace prize.

Mr Yu said he had been grabbed by state security officers the day before the Nobel ceremony in 2010, hooded and beaten. “They stripped off all my clothes and pushed me naked to the ground and kicked me maniacally. They had a camera and were taking pictures as I was being beaten, saying with glee they would post the naked photos online,” he said.

Mr Yu said one of his attackers had told him: “If the order comes from above, we can dig a pit to bury you alive in half an hour and no one on earth would know.”